Abstract:In this study, corn starch and glutaric anhydride (GA) were used as the raw material and esterifying agent, respectively, to explore the effects of the initial starch slurry concentration, reaction time, reaction temperature, and pH value (during the preparation of starch glutaric acid ester in ethanol) on the degree of substitution. The conditions used to prepare GA starch were as follows: starch slurry concentration: 35% (m/m); reaction period: 3 h; reaction temperature: 35 ℃; and pH value of the reaction system: 8.5. The product was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). New absorption peaks corresponding to a C=O stretching vibration at 1733 cm-1 and -COO- antisymmetric stretching vibration at 1555 cm-1 were found in starch glutaric acid ester, indicating the successful esterification of starch molecules. Varying degrees of dents and ruptures were found on the granule surface of the modified starch. The XRD results revealed that the modified starch GA exhibited an A-type diffraction pattern, which confirmed that the reaction mainly occurred in the amorphous region. DSC revealed that the gelatinization temperature and enthalpy of the modified starch were decreased. Analysis by the Brabender viscosity method indicated that the peak viscosity of the modified starch was significantly increased.
